This invention relates generally to an inflatable restraint for an occupant of a motor vehicle and more particularly to an inflatable restraint that mitigates the potential of injury to a driver of a motor vehicle caused by late deployment of an airbag incident to a vehicle crash.
Late deployment is a condition that obtains when, for example, the driver of a vehicle has translated forwardly from his normal seated position behind the steering wheel of the vehicle to a point where his chest is either in close proximity to or in contact with an airbag module mounted centrally of the steering wheel at the time of initiation of inflation. In this situation the potential for injury from the crash is increased due to the opening force of the airbag module cover and deployment of the airbag against the driver's chest. The potential for injury is strongly correlated with the force with which the opening cover and deploying airbag impacts the vehicle occupant during the first 20 milliseconds of deployment.
It is known to control the opening force of the airbag module as well as the rate of bag deployment by controlling the burn rate of the gas producer during the first 10 to 15 milliseconds immediately following initiation. Initial gas production is limited to a relatively low level until opening of the airbag module cover after which pressurization is allowed to increase rapidly to complete deployment of the airbag.
Another method of controlling the opening force of an airbag module cover and airbag deployment is to provide an alternate path for the deploying bag to escape. This is done by changing the pattern and shape of the airbag cover so that if the front of the cover is loaded by the vehicle occupant, the airbag can escape by bursting out the sides of the cover. Gas pressure is relieved due to the increasing volume of the deploying airbag.
However, the aforesaid measures do not completely mitigate potential injury due to late deployment of an airbag.